This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Physical inactivity is associated with the accelerated loss of lean body mass and functional capacity. Our preliminary data demonstrate a 3-fold greater loss of lean leg mass in older individuals during 10 days of bed rest, compared to a cohort of younger adults during 28 days of bed rest. Further, in healthy young volunteers, the combined catabolic insults of physical inactivity and simulated stress (hypercortisolemia) resulted in a 300% greater loss of lean muscle mass than inactivity alone. These data highlight the potential for catastrophic loss of muscle mass and functional capacity in physically incapacitated, hospitalized older adults. The specific goal of this project is to quantify the magnitude of muscle loss experienced by an elderly patient population during a period of inpatient care in the Acute Care for Elders (ACE) Unit at UTMB. Body composition data (muscle and fat mass) will be obtained on admission and prior to discharge (typically 3-6 day period) using dual energy x-ray absorptiometry (DEXA). These descriptive data will be subsequently used to support NIH grant submissions focusing on targeted interventions to reduce muscle loss and improve functional recovery.